Linear correlation between the fractal dimension of surface EMG signals and the peak power of vertical jumps

We calculated the fractal dimension (FD) of surface EMG of seven right and left lower limb muscles of thirteen basket players, while performing squat and countermovement vertical jumps. The peak power, adjusted for body mass, was measured by means of a force platform. Significant linear correlation between FD and peak power was determined for six out of seven muscles, yet characterized by a rather high fraction of unexplained variance (65% to 88%). Mono-articular Vasti (lateralis and medialis) displayed the strongest correlation (
$R=0.472$
to 0.534), while bi-articular Rectus and Biceps femoris and Gatrocnemius medialis presented a comparable level of correlation (R around 0.364-0.466). In this work, FD analysis has been applied to a routine power test in realistic conditions. This experimental design permitted evaluate the feasibility and usefulness of the procedure. The high level of uncertainty associated to the correlations does not permit predictive results. However, FD con be useful to simply and quickly assess the level of participation of muscles or muscle groups in determining a performance. However, further researches are needed to refine and explore further potentiality of this technique.